[PATCH AUTOSEL 6.11 066/244] drivers/perf: arm_spe: Use perf_allow_kernel() for permissions

Sasha Levin
2024-09-25T11:39:19Z

From: James Clark <james.clark@linaro.org>

[ Upstream commit 5e9629d0ae977d6f6916d7e519724804e95f0b07 ]

Use perf_allow_kernel() for 'pa_enable' (physical addresses),
'pct_enable' (physical timestamps) and context IDs. This means that
perf_event_paranoid is now taken into account and LSM hooks can be used,
which is more consistent with other perf_event_open calls. For example
PERF_SAMPLE_PHYS_ADDR uses perf_allow_kernel() rather than just
perfmon_capable().

This also indirectly fixes the following error message which is
misleading because perf_event_paranoid is not taken into account by
perfmon_capable():

$ perf record -e arm_spe/pa_enable/

Error:
Access to performance monitoring and observability operations is
limited. Consider adjusting /proc/sys/kernel/perf_event_paranoid
setting ...

Suggested-by: Al Grant <al.grant@arm.com>
Signed-off-by: James Clark <james.clark@linaro.org>
Link: https://lore.kernel.org/r/20240827145113.1224604-1-james.clark@linaro.org
Link: https://lore.kernel.org/all/20240807120039.GD37996@noisy.programming.kicks-ass.net/
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/perf/arm_spe_pmu.c | 9 ++++-----
include/linux/perf_event.h | 8 +-------
kernel/events/core.c | 9 +++++++++
3 files changed, 14 insertions(+), 12 deletions(-)

diff --git a/drivers/perf/arm_spe_pmu.c b/drivers/perf/arm_spe_pmu.c
index 9100d82bfabc0..3569050f9cf37 100644
--- a/drivers/perf/arm_spe_pmu.c
+++ b/drivers/perf/arm_spe_pmu.c
@@ -41,7 +41,7 @@

/*
* Cache if the event is allowed to trace Context information.
- * This allows us to perform the check, i.e, perfmon_capable(),
+ * This allows us to perform the check, i.e, perf_allow_kernel(),
* in the context of the event owner, once, during the event_init().
*/
#define SPE_PMU_HW_FLAGS_CX 0x00001
@@ -50,7 +50,7 @@ static_assert((PERF_EVENT_FLAG_ARCH & SPE_PMU_HW_FLAGS_CX) == SPE_PMU_HW_FLAGS_C

static void set_spe_event_has_cx(struct perf_event *event)
{
- if (IS_ENABLED(CONFIG_PID_IN_CONTEXTIDR) && perfmon_capable())
+ if (IS_ENABLED(CONFIG_PID_IN_CONTEXTIDR) && !perf_allow_kernel(&event->attr))
event->hw.flags |= SPE_PMU_HW_FLAGS_CX;
}

@@ -745,9 +745,8 @@ static int arm_spe_pmu_event_init(struct perf_event *event)

set_spe_event_has_cx(event);
reg = arm_spe_event_to_pmscr(event);
- if (!perfmon_capable() &&
- (reg & (PMSCR_EL1_PA | PMSCR_EL1_PCT)))
- return -EACCES;
+ if (reg & (PMSCR_EL1_PA | PMSCR_EL1_PCT))
+ return perf_allow_kernel(&event->attr);

return 0;
}
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 1a8942277ddad..e336306b8c08e 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1602,13 +1602,7 @@ static inline int perf_is_paranoid(void)
return sysctl_perf_event_paranoid > -1;
}

-static inline int perf_allow_kernel(struct perf_event_attr *attr)
-{
- if (sysctl_perf_event_paranoid > 1 && !perfmon_capable())
- return -EACCES;
-
- return security_perf_event_open(attr, PERF_SECURITY_KERNEL);
-}
+int perf_allow_kernel(struct perf_event_attr *attr);

static inline int perf_allow_cpu(struct perf_event_attr *attr)
{
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 8a6c6bbcd658a..b21c8f24a9876 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -13358,6 +13358,15 @@ const struct perf_event_attr *perf_event_attrs(struct perf_event *event)
return &event->attr;
}

+int perf_allow_kernel(struct perf_event_attr *attr)
+{
+ if (sysctl_perf_event_paranoid > 1 && !perfmon_capable())
+ return -EACCES;
+
+ return security_perf_event_open(attr, PERF_SECURITY_KERNEL);
+}
+EXPORT_SYMBOL_GPL(perf_allow_kernel);
+
/*
* Inherit an event from parent task to child task.
*
--
2.43.0